CODEWITHSUNDEEP
couchdbmapreduce
Patrick Klingemann
Patrick Klingemann

Reputation: 9014

couchdb - retrieve documents for which an id is not included in an array property

I have the following document structure in a couchdb database:

{
  'type': 'Message',
  'subject': 'Cheap V1@gr@',
  'body': 'not spam',
  'metadata': {
    'participation': {
      'read': [1,2,3]
    }
  }
}

The read array is a list of user ids who have read a message. I can easily create a view to allow me to filter the list of messages by the messages a user has read, like so:

Map function

function(doc) {
  doc['metadata']['participation']['read'].forEach(function(user_id) {
    emit(user_id, doc._id);
  });
}

and then to execute the query for user_id = 1:

curl -X GET \
  http://localhost:5984/couchrest/_design/Message/_view/included_in_read?key=1

My question is: how would I go about writing a view/query to return documents for which the user's id is NOT included in the read array, i.e. "unread" messages.

Upvotes: 2

Views: 616

Answers (2)

JasonSmith
JasonSmith

Reputation: 73722

You need to use a technique called the Thai massage.

The link above is my description of it in an email, and I described it in an answer to a similar question on Stack Overflow: Find CouchDB docs missing an arbitrary field

I think the variation you would need to do is emit a 2-array for the key, [user_id, doc_id]. When you query for "hits" for user 1234, use ?startkey=[1234,null]&endkey=[1234,{}] to show only the hits for that user.

Upvotes: 1

Aruna
Aruna

Reputation: 103

You can use the following Map function, 

 function(doc) {
   if(!doc.metadata.participation.read)
     emit(doc.user_id, doc);
  }

and then to execute the query for user_id = 1:

curl -X GET \
http://localhost:5984/couchrest/_design/Message/_view/included_in_read?key=1

Upvotes: 0

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